Broadband CPW-fed slot antenna with circular polarization for on-body applications at ISM band

A broadband coplanar waveguide (CPW) fed antenna which has circular polarization is presented. The antenna is designed to operate at the frequency band (2.45 GHz) that is widely used for industrial, scientific and medical (ISM) applications. The proposed antenna has a uniplanar structure. A square slot is created in the ground which is located at the top layer of a printed circuit board. The CPW feeder is connected to a horseshoe shaped radiator inside the square slot. The circular polarization of the antenna is achieved through inserting T- and L-shaped strips inside the slot. The proposed antenna has a 3 dB axial ratio bandwidth from 2.1 GHz to 2.67 GHz, i.e. 20% fractional bandwidth, and impedance matching bandwidth from 1.5 GHz to 3.15 GHz, which is equivalent to 67.5% fractional bandwidth. The whole structure of the proposed antenna has a compact size of 40 mm × 40 mm.